I like the primo diaphram mouth calls.  A little tricky at first, but once you get the hang of it they are great to have in the field.  Can also use them to make cow calls so keeps the elk guessing.

In a lot places elk are bugled at constantly by guys on ATVs.  I'm of the opinion that unless you really know what you're doing, you probably don't want to bugle at all.  In most places, I wouldn't bugle unless it was way before dawn or after dusk, just to make sure there are elk in the area.

If they are bugling you should be able to move in on them.  More often than not, it's going to be a little guy, and any good sounding bugle may scare him off.

Ex. is correct, get a cow call to call the elk in closer. I only bugle to locate bulls most of the time. Some times you might bugle to pick a fight with a bull, then i'll rake a tree and bugle, he will either come to fight or gather his cows and split. Primo's has a nice (pack bugle) its not to big and does'nt let you sound to big either.

I have a Primos Terminator. I use it for a locator and then cow cow cow call.

I agree with Ex, unless you have time to go out and learn how to do it and get away from the other hunters then the bugle is not worth that much.  Now a cow call and I can't believe I am saying this but the Hoochie MaMa is one of the best out there will work quite well.  I have seen spike bulls run over a half mile to me after I have used it.